Aromatic sulfone polymers (such as polyphenylsulfone (PPSU), polyethersulfone (PESU) and bisphenol A polysulfone (PSU)) have been widely used in applications where their outstanding properties have been valued. These properties include dimensional stability, low coefficient of thermal expansion, retention of modulus at high temperature, radiation resistance, hydrolytic stability and tough mechanical properties. Such applications include articles as various as plumbing, commercial aircraft interiors, cookware, wire insulation and food service articles. For instance, polyphenylsulfone (PPSU) is a commonly used polymer in applications such as plumbing, medical and aerospace applications.
However, despite outstanding resistance to hydrolysis these polymers are also subjected to specific chemical environments which can cause environmental stress cracking due to either long or short term exposure to various chemicals. These chemical environments include for example aggressive surfactants or polyurethane curing agents for the plumbing applications, cleaning and sterilization reagents for the medical materials applications. Moreover, these later are facing more and more stringent cleaning and sterilization requirements.
There is thus a need in the art to provide new polymers featuring all the superior properties of aromatic sulfone polymers, such as hydrolytic stability and tough mechanical properties, while also performing outstanding chemical resistance.
Precisely, aromatic ketone polymers offer an exceptional balance of technical properties, namely high melting point, excellent thermal stability, high stiffness and strength, good toughness and really excellent chemical resistance. However, the somewhat low glass transition of these materials limits theirs use in certain specific applications where the use temperature is above 170° C. Moreover, their high costs preclude their use in many commodity markets.
Prior art documents describe various attempts to combine the most advantageous properties of aromatic ketone polymers with the ones of aromatic sulfone polymers.
WO 2007/071780 in the Applicant's name describe the use of an effective amount of a poly(biphenyl ether sulfone) for diluting a poly(aryl ether ketone) making available polymer compositions with a lower cost than that of poly(aryl ether ketone) compositions, and featuring a chemical resistance at least substantially the same as the one obtained by said poly(aryl ether ketone) compositions.
Unfortunately, those blends still suffer from poor intrinsic properties, such as opacity, due to their nature of blends. Besides, the properties of blends are typically dependent on the processing conditions that can impact their morphology while the invented polymer does not display this sensitivity.